Image forming apparatuses are devices for forming images on printing media according to input signals, and examples thereof include printers, copiers, facsimiles, and all-in-one devices implemented by a combination thereof.
One type of image forming apparatus, an electrophotographic image forming apparatus, includes a photosensitive unit having a photoreceptor therein, a charging unit which is disposed near the photosensitive unit and charges the photoreceptor to a predetermined potential level, a developing unit having a developing roller, and a light scanning unit. The light scanning unit applies light onto the photoreceptor charged to the predetermined potential level by the charging unit to form an electrostatic latent image on a surface of the photoreceptor, and the developing unit supplies developers onto the photoreceptor, on which the electrostatic latent image is formed to form a visible image.
In the case of the image forming apparatus having a structure in which a developing roller is in contact with a photoreceptor to supply a developer, the developing roller and the photoreceptor have to be in contact with each other when a printing operation is performed, and the developing roller and the photoreceptor have to be separated from each other to prevent interference between the developing roller and the photoreceptor when the developing unit is replaced.